
297Physical Security Management
This very basic principle is used throughout physical security and has some
very simple rules to it. First, the means of successfully passing through the various
controls should be different and not subject to the same vulnerability. It is fairly
useless to have two levels of access control where the same card can be used to
open both. The second is that each layer of defense should operate independently
of the results of the area outside of the area it is protecting. What this intends
to say is that just because you present yourself at the control does not mean that
you can assume that you will be given access ...